can someone tell me in a nutshell WHAT the difference is in using E-E center-GAPPED(2.5mm) ferrite core -versus- no gap E-E core??

I have a real big core here..

wish to drive core at about 90KHz....TL494 in complementary output...

best Regards,
Raff

luka

4th October 2006 08:10 PM

The flux in core will be larger if there is no gap.Gap cores can store much more energy and are also used as choke.

RX5

4th October 2006 11:02 PM

Hi,

so meaning having a GAP in such a core is a good thing for SMPS??

I have done my previous SMPS with NO GAPs.... I dont have idea how it would be if core HAD gaps.. :rolleyes:

sawreyrw

4th October 2006 11:02 PM

Ungapped cores will easily saturate (bad) if there is any volt second imbalance (or DC current) in them. That's why almost all inductors (not transformers) use a gap. Push pull transformers sometime use a gap for the reason mentioned above. As an aside, volt second imbalance can be avoided by using current mode control in push pull circuits.

RX5

4th October 2006 11:07 PM

Quote:

Originally posted by sawreyrw Ungapped cores will easily saturate (bad) if there is any volt second imbalance (or DC current) in them. That's why almost all inductors (not transformers) use a gap. Push pull transformers sometime use a gap for the reason mentioned above. As an aside, volt second imbalance can be avoided by using current mode control in push pull circuits.

ok... so in push-pull operations using gapped, how about turns? i mean do I have to add more (as compared to ungapped)??

A gapped transformer doesn't need more turns, but the magnetizing current will be larger. The flux swing will be the same regardless of the gap. The magnetizing currents will cause slightly higher I^2*R losses, but this is not normally a big deal. Likewise, the current through the switches will be larger. You do need to check the power losses associated with this.

The leakage inductance will be about the same whether or not there is a gap, so the losses associated with them should be the same.

RX5

4th October 2006 11:54 PM

ah ic... so THESE slightly higher I^2*R losses , would be a bit heating of winding, am I correcT? :)

and I think with such slight? heating would mean Higher temp with Driver MOSFETs?

so, i mean WHAT would I normaly expect to get if I changed my working SMPS with a GAPPED core?